This invention relates to an electronic circuit for use in dividing a dividend by a divisor to calculate a quotient and, in particular, to an electronic circuit capable of calculating the quotient by the use of an approximate reciprocal of the divisor.
As will later be described with reference to one of several figures of the accompanying drawing, an electronic circuit of the type described is proposed by H. Matsumoto in Japanese unexamined patent publication No. Syo 57-41,737, namely, 41,737/1982. With the electronic circuit, it is possible to calculate an eventual quotient which has a plurality of digits, N in number, for g-ary numbers and which is divisible into first through N-th partial quotients for the respective digits.
More particularly, the proposed electronic circuit carries out current division between a dividend and a divisor with reference to an approximate reciprocal of the divisor and a correction factor which is given by a product between the approximate reciprocal and the divisor and is therefore nearly equal to unity. The correction factor is therefore calculated by a multiplying circuit. Subsequently, the dividend is multiplied by the approximate reciprocal by the multiplying circuit to produce a primitive quotient which is equal to a product between the dividend and the approximate reciprocal. Thereafter, the primitive quotient is processed by the multiplying circuit into the first through the N-th partial quotients in accordance with a predetermined algorithm.
Anyway, the multiplying circuit may be an adder and should repeatedly be used to calculate the correction factor, the primitive quotients, and so on. Consequently, the next following division can not be started until the current division is finished. Thus, the electronic circuit can not achieve a high throughput on processing the division.
In Cray-1S SERIES HARDWARE REFERENCE MANUAL HR-0808 published 1980, 1981, by Cray Research Inc., Newton's method is used to accurately calculate a reciprocal of a divisor. The calculation of the reciprocal is carried out in a so-called pipeline method at a high speed. Although the reciprocal is accurately calculated, an objectionable error takes place such that a final residue becomes negative.